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Brass Furnace.

a f/l

In bringing this chapter on casting and moulding to a close,
a few practical points will be mentioned, although it should be
clearly understood that perfect practice can only be obtained by
actual work on such articles as have been mentioned in the text

The Size of Gates, and the number of them, can only be
determined by constantly watching the results obtained from
previous work.

Flat gates  should be avoided as much as possible, as
they tend to clog, though sometimes they are beneficial when
they are required to break off easily without damaging the
casting. Fig. 51 is intended to represent diagrammatically the
different gates and channels used to supply a mould; the pour-
ing gate; the skimming gate, for the purpose of retaining the
scum (and here some ingenuity is required to keep the latter
in the skimming gate by centrifugal action, the whirling being
produced by admitting the metal at a tangent); the sprues or
connexions from skimming gate to mould (they may be of any
number considered necessary); the feeding gate or gates, the
use of which is to fill up any part of the casting which is likely
to shrink; and the risers, which are to allow the whole of the
air in the mould to pass out and so prevent blow-holes, the